| 1. |
- Kalliomäki, Jarkko, et al.
(författare)
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Multiple spinal pathways mediate cutaneous nociceptive C-fibre input to the primary somatosensory cortex (SI) in the rat.
- 1993
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Ingår i: Brain Research. - 1872-6240. ; 622:1-2, s. 271-279
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, partial lesions of the lower thoracic spinal cord in rats anaesthetized with halothane and nitrous oxide were made in order to elucidate which of the spinal funiculi mediate a nociceptive C fibre input to SI. Field potentials evoked by noxious CO2-laser stimulation were recorded in the left SI. Nociceptive C fibre input from the right hindpaw to SI was propagated by the dorsal funiculi (DF) and the left and right lateral funiculi (LLF and RLF, respectively). Nociceptive C fibre input from the left hindpaw was propagated by LLF and RLF, but not DF. Input from the hindpaws mediated by LLF and RLF caused widespread surface positive potentials throughout most of SI, although potentials in the hindlimb area tended to be larger than those in other areas of SI. Input from the right hindpaw mediated by DF caused surface positive potentials mainly in the hindlimb area of SI. Intracortically, the field potentials reversed polarity in the superficial laminae and had maximal negative amplitudes in laminae III-IV (input transferred by DF and LLF) and in laminae V-VI (input transferred by LLF and RLF). It is concluded that there are multiple spinal pathways which can transfer information from cutaneous nociceptive C fibres to SI in the rat. These ascending pathways seem to activate partly different thalamo-cortical systems.
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| 2. |
- Kalliomäki, Jarkko, et al.
(författare)
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Nociceptive C fibre input to the primary somatosensory cortex (SI). A field potential study in the rat.
- 1993
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Ingår i: Brain Research. - 1872-6240. ; 622:1-2, s. 262-270
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, noxious thermal stimulation of the skin with short pulses of CO2-laser radiation was used to identify a cutaneous nociceptive C fibre input to SI and investigate the organization of this input in halothane-nitrous oxide anaesthetized rats. Noxious CO2-laser stimulation of the glabrous skin of the hindpaw consistently evoked late surface positive field potentials in SI (average onset latency 226 ms, peak latency 296 ms). It was demonstrated that these late potentials were evoked by an input from nociceptive C fibres, using a combination of latency measurements, anodal block of A fibre conduction and graded intensities of stimulation. Compared to the tactile evoked potentials in SI, the nociceptive C fibre evoked potentials were more widespread and exhibited a crude somatotopical organization. Intracortically, both tactile and nociceptive C fibre evoked potentials reversed polarity and exhibited a peak negativity in laminae III-IV. The nociceptive C fibre evoked potentials exhibited an additional peak negativity in laminae V-VI. The latter potential had a different time course as compared to the nociceptive C fibre potential evoked in laminae III-IV. In conclusion, an input from cutaneous nociceptive C fibres to SI was demonstrated for the first time in animal experiments. The input to SI from tactile receptors and cutaneous C nociceptors were differently organized.
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| 3. |
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| 4. |
- Schouenborg, Jens, et al.
(författare)
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Modular organization of spinal nociceptive reflexes : A New Hypothesis
- 1994
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Ingår i: News in Physiological Sciences. - : American Physiological Society. - 1522-161X. ; 9, s. 261-265
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Forskningsöversikt (refereegranskat)abstract
- Recent experimental studies suggest that the nociceptive withdrawal reflex system essentially has a "modular" organization, with each module concerned with the control of a single or a small group of muscles. This organizational principle appears to apply also to some spinoolivocerebellar pathways.
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| 5. |
- Weng, Han Rong, et al.
(författare)
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GABA(A) receptor blockade inhibits Aβ fibre evoked wind-up in the arthritic rat
- 1998
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Ingår i: NeuroReport. - : Ovid Technologies (Wolters Kluwer Health). - 0959-4965. ; 9:6, s. 1065-1069
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Tidskriftsartikel (refereegranskat)abstract
- To clarify the mechanisms of allodynia we have examined whether 'wind- up' of nociceptive withdrawal reflexes (NWR), a phenomenon characteristic of nociceptive C fiber spinal processing, can be mimicked by stimulation of tactile Aβ fibers in monoarthritic decerebrate spinal rats. Knee joint monoarthritis was induced by carrageenan/kaolin under halothane anaesthesia 5 h before recordings. In arthritic, but not in control rats, wind-up of NWR of the semitendinosus muscle could be evoked by repeated stimulation of Aβ fibres. By contrast, peroneus longus reflexes did not exhibit marked wind- up. Bicuculline (0.03-0.3 mg/kg, i.v.) dose-dependently inhibited this wind- up. Hence, reflex wind-up can be elicited by tactile Aβ fibers in arthritic rats through a GABA(A) dependent mechanism.
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| 6. |
- Weng, Han Rong, et al.
(författare)
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Nociceptive inhibition of withdrawal reflex responses increases over time in spinalized rats
- 1996
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Ingår i: NeuroReport. - : Ovid Technologies (Wolters Kluwer Health). - 0959-4965. ; 7:7, s. 1310-1314
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Tidskriftsartikel (refereegranskat)abstract
- Time-dependent changes of nociceptive inhibition of hindlimb withdrawal reflex (WR) pathways were investigated in acute decerebrate spinal rats. Electromyographic recordings of WR of peroneus longus and extensor digitorum longus muscles were made. For each muscle, both short and long latency WR evoked by subcutaneous electrical stimulation and WR evoked by noxious pinch could be inhibited by noxious CO2 laser stimulation of a specific skin area of the ipsilateral hindlimb. The inhibitory effects and size of the inhibitory receptive fields increased spontaneously between two- and three- fold during the first 12 h after spinalization. The functional and possible clinical significance of the strengthened nociceptive inhibitory control and mechanisms underlying the changes of this control after spinal transection are discussed.
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